Nitrates feed algae and keep your chlorine from holding — and no chemical removes them. Here’s what they are, where Florida pools pick them up, and the dilution treatment plan that actually brings them down.
Nitrates are dissolved nitrogen — invisible, tasteless, and one of the most stubborn reasons a pool fights you all season.
Nitrates are nitrogen — a primary algae nutrient. A pool can test perfect for chlorine and pH and still keep going green, because the algae has all the food it needs to outpace your sanitizer.
High nitrates make chlorine demand soar. You keep adding chlorine and it keeps vanishing, because it’s being burned up faster than you can add it. Until the nitrates come down, it’s a reading you can’t hold.
This is the key difference from phosphates: a phosphate remover precipitates phosphates out, but there is no additive that takes nitrates out of pool water. The only effective fix is dilution — draining and refilling.
Knowing the source is half the fix — because once you’ve diluted them out, you want to keep them from coming back.
Tap water — and especially well water around Pinellas — can carry nitrates straight into your pool every time you top off. A pool that’s topped up all summer slowly concentrates them.
Lawn fertilizer is mostly nitrogen. Rain and irrigation wash it off the grass and flower beds and carry it right into the pool — a common culprit on well-kept Florida yards.
Heavy Gulf-coast storms pull nitrogen out of the air and rinse it off surrounding surfaces into an open pool. A wet season can move the needle on its own.
Decaying leaves, grass clippings, and pet or wildlife waste all break down into nitrogen compounds in the water — a steady trickle that adds up between drains.
If any of these sound familiar, stop pouring chlorine into the problem — it’s money down the drain until the nitrates come down. It’s time to get the water tested.
There’s no chemical shortcut for nitrates. Here’s the exact, measured process we use to bring a high-nitrate pool back — and keep it there.
Nitrates don’t show up on a standard chlorine/pH test. We use a dedicated nitrate test for an actual ppm reading — above ~10 ppm is where algae and chlorine demand take off.
Removal is pure dilution: replace half the water and the reading drops by roughly half. We measure your gallons and work out exactly how much to drain to reach a safe level — no guessing.
We lower the pool to the calculated level and refill with fresh, low-nitrate water — done carefully to protect the plaster or liner and avoid floating the pool out of the ground.
Fresh fill water resets everything. We re-balance chlorine, pH, alkalinity, and stabilizer (CYA) so the pool comes back swim-ready, not just diluted.
We pin down the source — usually fill water or lawn runoff — and adjust your routine so nitrates don’t quietly creep back up between visits.
The questions homeowners ask most about high nitrates. See all FAQs →
No. Unlike phosphates, there is no additive that removes nitrates from pool water. The only effective fix is dilution — partially draining and refilling with low-nitrate water.
Aim for under 10 ppm. Above that, nitrates start fueling algae and pushing chlorine demand up; problem pools often test 20–50+ ppm.
Nitrate dilution is linear: draining and replacing about half the water roughly halves the reading. We measure your gallons and calculate the exact percentage to reach a safe level.
High nitrates feed algae around the clock, so chlorine gets consumed as fast as you add it. Until the nitrates come down, you’re chasing a reading you can’t hold.
If your water’s been a constant battle, just mention nitrates to your Suncoast tech — we’ll test for it on your next visit and put together a plan. Questions in the meantime? Reach us anytime at (727) 295-3621.